Holding Area

A holding area at Ashio Copper Mine sits on one of the lower levels of the processing plant, where intermediate product was stored between processing stages. The area is a concrete-floored bay enclosed on three sides by the structural walls of the building, with the fourth side open onto the working floor. Steel partitions divide the bay into sections, each one sized for a different intermediate product. Some of the bays still hold residual material: pale-grey crushed ore in one, darker concentrate in another. A small overhead crane runs above the bays, the hook parked at one end of its rail. The light is dim; the windows on the side wall are partly obscured by the bay walls.

Holding areas in a mineral processing plant buffer the working stages from each other. When upstream production gets ahead of downstream demand, the intermediate product accumulates in the holding bays; when downstream draws faster than upstream can supply, the bays drain down. The arrangement keeps the plant running through short-term mismatches. Ashio used holding bays of this kind throughout the working life of the works under Furukawa modernisation from 1877 to the Excavation Department's 1973 closure. The residual material in the bays in this photograph is the last batch that came through the plant.